Recent years, each IT system (IT is an abbreviation for Information Technology, and hereinafter, an IT system is also referred to as an information processing system) has become complex and large-scaled because various IT apparatuses (hereinafter, also referred to as information processing apparatuses) are coupled thereto via a network. Faults may affect the various IT apparatuses via the network. As an example of root cause analysis technologies of identifying the locations and causes of the faults, Patent Document 1 discloses an event correlation technology of analyzing a fault location and a cause by using event information used by an IT apparatus to notify fault contents. The event correlation technology is also called a technology of estimating a root cause by using the correlation of events sent from computers when faults occur. Non-Patent Document 2 discloses a technology in which a rule is made from a combination of the technology disclosed in Patent Document 1 and events occurring at the time of faults, and an estimated root cause, handled as a pair, thereby quickly determining a root cause by using an inference engine made based on an expert system.    [Patent Citation 1] U.S. Pat. No. 6,249,755 Specification    [Non Patent Citation 1] “Rete: A Fast Algorithm for the Many Pattern/Many Object Pattern Match Problem”, ARTIFICIAL INTELLIGENCE, Vol. 19, no. 1, 1982, pp. 17-37.